Discovery of Passively Stable Flapping Flight and Analytical Criteria for Flight Stability

The vastness of the morphological and dynamical space explored by nature's flying animals makes it extremely challenging to identify the specific criteria required for successful flyers. We construct an efficient flapping flight model to facilitate the exploration of this large flight space. The first surprise of our simulations is the discovery of a region of passively stable upward flight. Analyzing the boundary of stability region lead to analytical criteria. These new criteria provide basic rules for designing stable robotic flyers, which so far has eluded us.